Spectacle frames used by people above 40 years of age are provided with 2 types of lenses which are meant to give clear distant vision (>100 cms) and near vision (33-50 cms). These bifocal glasses are in use for many years.
Along with this as already known, a group of people in few occupations especially computer users need an extra lens to enable them to clearly visualize the monitor which lies at the intermediate zone (50-100 cms).
As already known in the prior art, this third power is provided in a separate spectacle frame or is incorporated into the regular unifocal or bifocal spectacle frame replacing either one or both of the two powers providing only one or two zones of vision at a time. Particularly, bifocal glass wearers using computers either manage with the regular bifocal glasses putting up with the problems as mentioned below or carry separate computer eye glasses with the lens for intermediate vision, which is annoying. This requires repeated glass changing which is a nuisance.
The problems with the existing multifocal spectacle frames during computer usage are as follows                1) Inability to clearly visualize the computer monitor, embroidery machine etc. at a comfortable working distance.        2) To see the computer monitor people using only bifocal spectacles tend to acquire a peculiar neck position by lifting their chin up while trying to visualize the monitor through the near vision lens, which causes strain to the eyes, neck and the back resulting in chronic medical and surgical problems like back pain, headache, neck pain etc. which comprises the computer vision syndrome (CVS) in the ophthalmic terminology.        3) The strain reduces work efficiency and hampers long hours of working which is inevitable in the present pattern of jobs.        
The already existing multifocal lenses like progressive lenses in a single frame according to prior art have a series of compromises like distortions and aberrations. These problems are occurring because the optical centers of distant and intermediate vision lenses do not overlap with each other and coincide with the pupillary center of the eye. There are peripheral vision distortions and aberrations due to the astigmatic curves. There is only a narrow central corridor of optimum vision which is not convenient for reading. This is not only expensive but also needs expertise for fitting. These glasses also pose a problem and do not give relief when the user does not need three zones of vision at any particular moment.
In the prior art mobile frames were used only for bifocals or monofocals or make up glasses. None of the mobile frames serve as trifocals in the prior art, and none of them were suitable or designed for computer use.
In these respects, this invention overcomes each of the above mentioned disadvantages of designs of the prior art as a computer eye glass. It is also substantially different from the existing eye glasses and is a definite improvement over the existing art as aforementioned.